drm/i915/guc: Simplify intel_guc_init_hw()

drm/i915/guc: Simplify intel_guc_init_hw()

Current version of intel_guc_init_hw() does a lot:
 - cares about submission
 - loads huc
 - implement WA

This change offloads some of the logic to intel_uc_init_hw(), which now
cares about the above.

v2: rename guc_hw_reset and fix typo in define name (M. Wajdeczko)
v3: rename once again
v4: remove spurious comments and add some style (J. Lahtinen)
v5: flow changes, got rid of dead checks (M. Wajdeczko)
v6: rebase
v7: rebase & onion teardown (J. Lahtinen)

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>